I have had this issue recently, too. It came on after I tested the 13” M2 MacBook Pro Touchbar that was recommended. I thought it may have been a coincidence…I only used the device two days in a row for 20 minutes. The Apple Silicon GPU dithering causes tachycardia - I can feel it when I enable/disable dithering with Stillcolor. I have POTS and dysautonomia, though, so I am pre-disposed to nervous system issues.
Do you occasionally get slight dizziness when looking down at a screen and then looking up or away? I’ve gotten that after having the flu in January. Wondering if I got reinfected with COVID recently and that’s playing a role, too, as my issues get worse with viral infections. I think the focusing issues is triggered by dithering.